<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        body {
            margin: 0;
            padding: 0;
        }

        .slider {
            width: 100%;
            height: 100vh;
            display: flex;
            background: url('./img/landscape-5009868__340.webp') no-repeat;
            background-position: 0 center;
            background-size: 100vw;
            position: relative;
        }

        .slider input {
            -webkit-appearance: none;
            width: 100%;
            background: none;
            z-index: 10;
        }

        .slider input::-webkit-slider-thumb {
            -webkit-appearance: none;
            width: 10px;
            height: 100vh;
            background-color: #111;
            cursor: pointer;
        }
        .original-image {
            position: absolute;
            left: 0;
            width: 20%;
            height: 100vh;
            background: url('./img/landscape-5072202__340.webp') no-repeat;
            background-position: 0 center;
            background-size: 100vw;
        }
    </style>
</head>
<body>
    <div class="slider">
        <div class="original-image"></div>
        <input type="range" value="20" max="100">
    </div>

    <script>
        document.querySelector('.slider input').addEventListener('input', function(){
            document.querySelector('.original-image').style.width = this.value + '%'
        });
    </script>
</body>
</html>